This application seeks renewal of the program for training veterinarians to become scientific leaders in comparative medicine. The best research training occurs when a highly motivated trainee works in the laboratory of an experienced externally funded mentor. The primary goal is to impart the knowledge, work habits, and research skills that will enable trainees to conduct research to advance knowledge in biology and comparative medicine. The current renewal outlines the research training program that emphasizes a ninety percent research effort over the entire three year period supported by the NIH. Trainees will normally spend at least four years in the training program and additional years to obtain the Ph.D. degree. A strength of the program is the intensive first year of clinical and residency training in laboratory animal medicine and pathology funded entirely by institutional funds. The succeeding three years, funded by this grant, will be devoted to graduate courses and a mentor relationship with an active, well-funded scientist and full participation in a research project. During this period, trainees will be guided by their research mentors and a Research Training Advisory Committee. This committee, composed of excellent biomedical scientists from several departments, is a major feature of the application. The training faculty consists of faculty members from the Unit for Laboratory Animal Medicine (ULAM) and additional research mentors who are comparative medical scientists that have developed close scientific relationships with the ULAM faculty. The availability of these excellent mentors from ULAM, and a variety of Schools, including the School of Medicine, the School of Public Health and the School of Dentistry and a large number of departments including Epidemiology, Human Genetics, Internal Medicine, Pathology, Periodontics, Pharmacology, and Surgery is a major feature of this application. Additional strengths of the program include the medical school resources and environment which nationally ranks sixth in NIH extramural support, has over 26 NIH-sponsored training grants, provides excellent biomedical research core facilities, and ULAM, which has a long and successful history of training leaders in comparative medicine. Trainees must be graduate veterinarians with superior academic records and special research interests. Special emphasis is given to recruiting and training underrepresented minority trainees and women. Support for six trainees is requested. This proposal offers a unique opportunity to train veterinary scientists in a world-class research environment enabling them to become future scientific leaders in comparative medicine.